1. Field of the Invention
This application claims priority from Argentinean Patent Application Ser. No. P 20070104222.
The present invention relates to a new retrievable packer assembly for use in wellbores and employed for several operations that are carried out in wellbores such as oil wells, water wells, gas wells, injection wells and the like. More particularly, the invention provides a packer system or assembly for sealing a section of a casing into a wellbore with automatic packing actuated by pressure, an incorporated circulation valve, seal cups and resilient expandable seal rings that allow the system to be employed in conventional tubing or casing as well as in coiled tubing, and together or only with a retrievable plug.
2. Description of the Prior Art
Retrievable packer tools are well known in the art for sealing one or more sections of a tubing, a casing or a wellbore to carry out wellbore operations such as stimulation works, either acid stimulation or fracturing, cementing operations, pressure tests, etc. Some of the conventional packers need to be rotated in order to be anchored into the tubing, therefore they can not be employed in coiled tubing.
While there are other systems that can be operated in coiled tubing the same are affected by several drawbacks. For example, there is a packer having seal cups, namely the “Straddle Packer”, which must be assembled for a fixed predetermined length. This is a drawback because the length thereof must be shorter than the lubricator of the equipment in the continuous tubing.
This type of packing has two opposed sets of seal cups that allow for a hermetic sealing of the enclosed area. It is difficult to efficiently clean this kind of packer in case of undesired silting, as the fluids get enclosed between the two seal cups, thus hindering both washing and freeing and extracting operations.
Another type is the know pressure or tension packer working with an automatic anchorage system, usually referred to in the art as J-shaped guide or bracket or simply “J” for automatic cycling. This allows the jaw-drag-block bearing basket to fix against the casing or tubing by friction and by elevating the mandrel of the tool it is firmly attached to the cone. In this way, the tool is packed through pressure. The main disadvantage lies in the fact that the casing must be stressed in order to fix and pack the tool, thus imposing a limit to the tubing's capacity for resisting treatments pressure or putting the safety junctions in risk by traction. When the pressure and stress is applied inside the tubing the swelling will cause traction on the tool and tubing and consequently their operational lifespan is shortened by fatigue.
A third type of packer is the known seal cup Packer which comprises a piston-carrying sleeve support, and packing elements such as cups and plugs. The drawback of this model is that no fluids can be transported directly before treatment, as this tool's first reaction is to seal off by pressure differential caused by the direct contact between the seal cups and tubes. To make up for this disadvantage an additional valve has been added which entails the drawback of more threads and the deficiency of the valve when executing sand treatments, for hydraulic fractures, for example, because the sand stays in the valve blocking it, thus impeding future operations.